[3] In a career that encompassed six patrols, operating from 1 January 1917, UC-42 succeeded in sinking fourteen vessels totaling 9,877 GRT, and disabling a warship of 1,210 tons displacement.

Loud mechanical sounds, of "hammering" and "turbine-like noises" were reported and, believing this to be a U-boat, a marker buoy was dropped, followed shortly after by a depth charge.

When the sinking and identification of the submarine was reported, the British Admiralty requested an identifiable item from the vessel for verification purposes, and in December 1917 divers recovered the telephone buoy from the conning tower.

The Royal Navy's Naval Intelligence Department were aware of submarine's 1 September departure date from Belgium and were sceptical about the hammering and engine noises reported by TB 055.

The Admiralty reported that "The longest known cruise of a UC boat in home waters is 24 days, so UC-42 must have been dead long before TB 055 and Sarba dropped the depth charges".

[6] The wreck was relocated on 6 November 2010 by Irish divers Ian Kelleher, Niall O'Regan, Philip Johnston, Eoin McGarry and Timmy Carey [7] in just 27 metres (89 ft) of water off Roche's Point Co. Cork.

[9] A commemorative plaque was subsequently attached to the boat's stern and under International Maritime Law she is now a War Grave, untouchable and the responsibility of the Deutsche Marine.